JP2661048B2 - Speed detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detecting device capable of detecting a speed with high accuracy even when, for example, a rotating body is rotating at a high speed or a low speed. . (B) Conventional technology Conventionally, to detect the rotational speed of a rotating body such as a gear, a method based on how many teeth of a gear pass at a predetermined reference time interval, a so-called frequency measurement method, or a sufficiently high frequency reference There is a so-called period measurement method that uses a clock and determines how many clock signals enter during the passage of a tooth. (C) Problems to be Solved by the Invention Among the above-mentioned conventional speed detection techniques, the measurement by the frequency is performed by increasing the reference time interval in order to increase the accuracy when rotating at a constant speed. 1 / interval
There is a problem that accuracy when speed changes due to the time delay of 2 is impaired. On the other hand, when measuring by period,
There has been a problem that the number of clocks counted at high speed decreases, and the error increases even at constant speed. In view of the above, it is an object of the present invention to provide a speed detecting device capable of reducing a time delay as long as a speed to be measured can be obtained and capable of performing a measurement with high accuracy even at a high speed. (D) Means and action for solving the problem The rotation speed detecting device of the present invention detects a moving body (1) having an element (1a) whose property changes every predetermined moving distance, and detects a change in this element. A detector (2) for outputting a pulse signal, a reference clock generator (6), a first counter (4) for counting clock signals from the reference clock generator, and a A first comparator for outputting an output whose count value is equal to or greater than a predetermined value N;
A second counter (9) for counting pulses from the detector, a second comparator (10) for outputting an output every time the count value of the second counter reaches a predetermined value,
AND means (8) for receiving the output of the detector, the output of the first comparator and the output of the second comparator, and the contents of the first and second counters in response to the output of the AND means. And a latch circuit (12) for latching the data. In this speed detection device, when the moving object to be measured moves,
A pulse signal is output from the detector according to the speed,
The pulse is counted by the second counter. on the other hand,
The clock signal from the reference clock generator is counted by the first counter. And an output of the detector, a first comparator output indicating that the count value of the first counter has exceeded a predetermined value, and a comparator outputting an output each time the count value of the second counter has reached the predetermined value. The count value of the first and second counters is latched by the latch circuit by the AND output of the output, and is used as speed data. When the speed is low, while the detector outputs one pulse interval, the first counter counts a clock equal to or more than a predetermined value, so that rotation speed data can be obtained at each pulse interval. When the rotation speed is high, the detector outputs several pulses before the first counter counts a clock of a predetermined value. Therefore, the count value of the first counter is latched by the latch circuit every several pulse intervals. , Rotation speed data is obtained. Therefore, even at a high speed, a measurement result with the same accuracy as that at a low speed can be obtained. (E) Examples The present invention will be described in more detail with reference to the following examples. FIG. 1 is a block diagram of a rotation speed detecting device according to an embodiment of the present invention. In the drawing, a pickup 2 is disposed near the rotating gear 1 having teeth 1a arranged at equal intervals, and generates a pulse each time the tooth 1a passes by rotation. This pulse is shaped by the waveform shaping circuit 3, input to the counter 9, and input to the one-shot circuit 7. The output of the one-shot circuit 7 is given to one of the input terminals of an AND circuit 8. The output of the one-shot circuit 7 is a pulse having a sufficiently small width. On the other hand, a clock signal is generated from the reference clock source 6 and input to the counter 4. The output of the counter 4 is input to the comparator 5, and when the counter 4 counts the predetermined value N, the comparator 5 outputs (high) indicating that thereafter. further,
The output of the comparator 5 is applied to another input terminal of the AND circuit 8. The output of the counter 9 is input to the comparator 10. The comparator 10 outputs an output (high signal) when the counter 9 has a power of 1 or 2, and the output is applied to yet another input terminal of the AND circuit 8. When all of the outputs from the one-shot circuit 7, the comparator 5, and the comparator 10 are input as "high", the AND circuit 8 derives the output of "high" and triggers the latch circuit 12 by this signal. Thus, the latch circuit 12 latches the outputs of the counter 4 and the counter 9, that is, the count value. The count value latched by the latch circuit 12 is sent to the CPU 13 as rotation speed data. The output of the AND circuit 8 is also input to the delay circuit 11,
The output of the delay circuit 11 is input to the counters 4 and 9 with a slight time delay from the trigger signal to the latch circuit 12, and resets them. Next, the overall operation of this embodiment will be described. As the gear 1 rotates, a pulse signal is output from the waveform shaping circuit 3 each time the tooth 1a passes through the pickup 2, and is counted by the counter 9. On the other hand, the counter 4 also counts the clock signal from the clock source 6. When the rotation of the gear 1 is low, the period of the output pulse from the waveform shaping circuit 3 due to the passage of the tooth 1a of the gear 1 is large, 1 is counted in the counter 9, and the next second pulse is input. By this time, the counter 4 counts the clock signal N times or more. Therefore, when the next pulse is output from the waveform shaping circuit 3, the output of the one-shot circuit 7, the output of the comparator 5, and the output of the comparator 10 are input to the AND circuit 8 as “high”, and the high output is output. And derive
Trigger the latch circuit 12. As a result, the count value 2 of the counter 9 and the count value of the counter 4 are
After a delay time, the counters 4 and 9 are reset, and the above operation is repeated every time the tooth 1a passes.
The count value latched by the latch circuit 12 becomes rotation speed detection data. Next, when the rotation of the gear 1 is at a high speed, the period of the output pulse from the waveform shaping circuit 3 due to the passage of the teeth 1a of the gear 1 is small, so that 1 is counted in the counter 9 and then the second
The counter 4 has not counted the clock signal N times before the first pulse is input. Therefore, the comparator 5 does not output, so the AND circuit 8 does not output, and the latch circuit 12 is not triggered. Of course, the counters 4 and 9 are not reset. Eventually, when the counter 4 counts N or more clock signals, the comparator 9 thereafter outputs count powers of 2 and the pulse is output from the waveform shaping circuit 3. Outputs high signal and latch circuit
Trigger 12 At this point, the latch circuit 12 latches the count values of the counter 9 and the counter 4. In this case, the count value of the counter 4 is not one interval of the teeth 1a of the gear 1, but several intervals, so that the rotation speed can be detected without reducing the accuracy even at high speed. In the above embodiment, a rotating body is taken as an example of a moving body, but the present invention can also be applied to speed detection of a moving body moving toward a straight enemy. (F) Effects of the Invention According to the present invention, even in the case of high-speed rotation, the reference clock signal is counted a predetermined number or more, so that measurement can be performed with high accuracy without errors. In addition, when the measurement is performed using the CPU by the conventional periodic method, the interrupt interval to the CPU greatly changes due to the change in the rotation speed.However, in the present invention, the interruption is substantially constant regardless of the change in the rotation speed. It can be an interval.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a rotation speed detecting device according to an embodiment of the present invention. 1: Gear, 2: Pickup, 4.9: Counter, 5: 10: Comparator, 6: Reference clock source, 12: Latch circuit.

Claims (1)

(57) [Claims] A moving object having an element whose property changes at every predetermined moving distance, a detector which detects a change in this element and outputs it as a pulse signal, a reference clock generator, and counts a clock signal from the reference clock generator. A first counter that outputs a signal when the count value of the first counter becomes equal to or more than a predetermined value N, a second counter that counts pulses from the detector, and a second counter that counts pulses from the detector. A second comparator for outputting an output every time the count value of the counter reaches a predetermined value, AND means for receiving the output of the detector, the output of the first comparator and the output of the second comparator as inputs, and the AND means And a latch circuit for latching the contents of the first and second counters in response to the output of the speed detector.